We report 6 affected males in a 5-generation family with x-linked Simpson-Golabi-Behmel (SGB) syndrome. All had pre- and postnatal overgrowth with 2 adult males attaining heights over 195 cm. Other features included "coarse" face with hypertelorism, broad nasal root, cleft palate, full lips with a midline groove of the lower lip, grooved tongue with tongue tie, prominent mandible, congenital heart defects, arrhythmias, supernumerary nipples, splenomegaly, large dysplastic kidneys, cryptorchidism, hypospadias, skeletal abnormalities and postaxial hexadactyly. All affected individuals were of normal intelligence. One boy died at age 19 months of a neuroblastoma. The putative origin of the gene in this family was the maternal great grandmother of the propositus. Eight carrier females, who showed varying manifestations of the gene, have been identified. Anthropometric analysis has identified preliminary characteristic craniofacial dimensions in this syndrome. Molecular studies have shown a maximal lod score of 2.81 with no recombinants observed for the SGB-DXYS68 pairing, mapping the disorder to Xqcen-Xq21.3.